This invention relates to stents for supporting lumens in living tissue in order to help hold those lumens open. The lumen may be a blood vessel, a bile duct, or any other similar body conduit that is tending to improperly constrict as a result of disease or malfunction. The lumen may be a graft (whether natural or artificial) in any type of body conduit.
It is known to insert hollow tube-defining structures ("stents") into tubular body organs or structures such as blood vessels to help open and keep open those body structures. See Boneau U.S. Pat. No. 5,292,331 and Hillstead U.S. Pat. No. 5,135,536 for examples of metal stent structures. (These two references are hereby incorporated by reference herein.) Stents of these types are typically introduced into a blood vessel or other tubular body structure on the deflated balloon of a balloon catheter. When the stent is at the desired location in the tubular body structure, the balloon is inflated to circumferentially expand the stent. The balloon is then deflated and the catheter is withdrawn, leaving the circumferentially expanded stent in the tubular body structure, usually as a permanent prosthesis for helping to hold the tubular body structure open and prevent stenosis or restenosis of that body structure.
While stents and stent applications of the type described above have been found to work extremely well, there may be room for improvement (at least in some cases) in avoiding abrupt transitions between stented and unstented regions of a tubular body structure. Such abrupt transitions may trigger a body reaction at or near the transition. Avoiding abrupt transitions or reducing the abruptness of such transitions may therefore be more therapeutic.
In view of the foregoing, it is an object of this invention to provide improved structures and methods for stenting tubular body structures.
It is a more particular object of this invention to provide stent structures and methods which reduce the abruptness of the transitions between the stented region and the unstented regions in a tubular body structure in which the stent is employed.